Semi-submersible vessels of different kinds are used in connection with offshore operations. A common type of such a vessel comprises two parallel under-water hulls and an operating deck supported thereby by columns.
The operating deck is designed for carrying equipment and staff accomodations above the deck, and a comprehensive staying is required between the columns as such, and between the columns and the deck. Generally six columns are used, which together with the stays form a considerable resistance to flow, when the vessel is under way or is kept stationary, respectively, over a prospecting area or a drilling hole.
The object of the present invention is to simplify the construction in general, and to reduce the resistance to flow. A further object is to provide a possibility considerably to increase the safety against total loss. It is furthermore of interest to provide an embodiment having a small water-line area and a high and uniform inertia relative to all essential axes, which will facilitate the retention of the vessel in a desired position.